Answer: Depends on what you want to use it for.
If you want to regurgitate your last meal, you're probably hoping that it
is free of leaks that can cause unpleasantness and embarrassment. However,
if you're a bagophile, the absence of leaks is secondary. You're probably
more interested in the presence of an airline logo on the bag.

Ever notice how airline advertisements never tell you the truth? They never tell you that as a passenger you'll
be cooped up in a metal tube with 200 other people for the next twelve
hours, that the food is awful, the stewardesses never the same as the ones in the
advertisement, the seats are uncomfortable, you won't have enough legroom,
the person sitting next to you is overweight and snores, and that if you do manage to get some sleep, the
captain will wake you up with an announcement detailing your flight path
over Romania.

No, instead, they emphasize the
positives: the wonder of powered flight, the quality of the on-board
service (only in first class, mind you), the quality and efficiency of
their cabin staff, the exotic nature of their destinations.

Barfbags play a role in this deception. Airlines (at least non-US ones) love to
distract their passengers by decorating their bags with birds,
animals or plants. Some are
even identifable as real species -- my collection contains over 40 different
species.

I still haven't come across a barfbag that emphasizes
either the quality of the food (how about printing the menu on the bag?)
or the beauty of the cabin crew (how about a picture of a smiling
stewardess holding a bag, saying "I'm Baggia, fly me"?).

Birds are understandably popular, but most are too
stylized to recognize.

However, the discerning bagophile can readily identify
eagles (Accipitidrae): see
White
Eagle Aviation, LADE and Bouraq
(although the bouraq was actually the winged steed that took the Prophet
Muhammad to heaven).

The problem with this is that realistic
portraits of planes are readily identifiable: you wouldn't expect to see a
picture of a 747 jumbo on a plane made by Boeing archrival Airbus. So
airlines tend to rely on abstract portrayals:

A
small number of bags subtly refer to the joys of finally arriving at your
destination and getting out of the plane. So they show things like the sun
(Corsair, National
Airlines) or the stranded starfish you'll find when you
finally stagger onto the beach (Eurocypria).

Another category refers back to the
country of origin. But they can't show a particular place -- a picture of
Big Ben would be out of place on a British carrier whose main aim is to
transport people away from Britain's miserable weather. So they show flags,
parts of flags, or the national colours (Air
France, Air UK, Air
Malta, Balkan, Crossair).

Finally, ever noticed that some airlines
have two versions of their logos: one for each side of the plane's
tailfin? The logos are mirror images of each other, and the bird, animal
or whatever never faces the back of the plane. This means that you can
always tell which way a plane is going by looking at the tailfin.

But bag designers haven't picked up on
this: I don't know of a single bag that has a mirror image of the
corporate logo on the reverse of the bag.